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| Roussel, Erwan; Sauvadet, Anne-laure; Chaduteau, Carine; Fouquet, Yves; Charlou, Jean-luc; Prieur, Daniel; Cambon, Marie-anne. |
| P>The distribution of the archaeal communities in deep subseafloor sediments [0-36 m below the seafloor (mbsf)] from the New Caledonia and Fairway Basins was investigated using DNA- and RNA-derived 16S rRNA clone libraries, functional genes and denaturing gradient gel electrophoresis (DGGE). A new method, Co-Migration DGGE (CM-DGGE), was developed to access selectively the active archaeal diversity. Prokaryotic cell abundances at the open-ocean sites were on average similar to 3.5 times lower than at a site under terrestrial influence. The sediment surface archaeal community (0-1.5 mbsf) was characterized by active Marine Group 1 (MG-1) Archaea that co-occurred with ammonia monooxygenase gene (amoA) sequences affiliated to a group of uncultured... |
| Tipo: Text |
Palavras-chave: Marine subsurface sediments; Sea floor biosphere; Gradient gel electrophoresis; Microbial communities; Molecular diversity; Anaerobic oxidation; Sequence alignment; Phylogenetic trees; Extracellular DNA; Methane hydrate. |
| Ano: 2009 |
URL: http://archimer.ifremer.fr/doc/2009/publication-6801.pdf |
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| Sultan, Nabil; Cochonat, Pierre; Foucher, Jean-paul; Mienert, J. |
| We present a theoretical study of the thermodynamic chemical equilibrium of gas hydrate in soil by taking into account the influence of temperature, pressure, pore water chemistry, and the mean pore size distribution. The model uses a new formulation based on the enthalpy form of the law of conservation of energy. The developed model shows that due to a temperature and pressure increase, hydrates may dissociate at the top of the hydrate occurrence zone to ensure a chemical equilibrium with the surrounding bulk water. This original result confirms what has been already shown through experiments. The second part of the paper presents an application of the model through a back-analysis of the giant Storegga Slide on the Norwegian margin. Two of the most... |
| Tipo: Text |
Palavras-chave: Storegga; Slope failure; GLE; Finite difference; Methane hydrate. |
| Ano: 2004 |
URL: http://archimer.ifremer.fr/doc/2004/publication-699.pdf |
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| Mazumdar, A.; Dewangan, P.; Joaeo, H. M.; Peketi, A.; Khosla, V. R.; Kocherla, M.; Badesab, F. K.; Joshi, R. K.; Roxanne, P.; Ramamurty, P. B.; Karisiddaiah, S. M.; Patil, D. J.; Dayal, A. M.; Ramprasad, T.; Hawkesworth, C. J.; Avanzinelli, R.. |
| We report evidence of paleo-cold seep associated activities, preserved in methane-derived carbonates in association with chemosynthetic clams (Calyptogena sp.) from a sediment core in the Krishna-Godavari basin, Bay of Bengal. Visual observations and calculations based on high-resolution wet bulk density profile of a core collected on board R/V Marion Dufresne (May 2007) show zones of sharp increase in carbonate content (10-55 vol%) within 16-20 meters below seafloor (mbsf). The presence of Calyptogena clam shells, chimneys, shell breccias with high Mg calcite cement, and pyrite within this zone suggest seepage of methane and sulfide-bearing fluid to the seafloor in the past. Highly depleted carbon isotopic values (delta(13)C ranges from -41 to -52% VPDB)... |
| Tipo: Text |
Palavras-chave: Methane hydrate; Cold seep; Authigenic carbonate; Bay of Bengal; AMO; Chemosynthetic community. |
| Ano: 2009 |
URL: https://archimer.ifremer.fr/doc/00218/32911/31414.pdf |
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| Minshull, T. A.; Westbrook, Graham; Weitemeyer, K. A.; Sinha, M. C.; Goswami, B. K.; Marsset, Bruno. |
| Methane hydrate—a solid substance in which methane is trapped within ice‐like crystals—is stable at low temperatures and high pressures and may be destabilized by ocean warming on both geological and human time scales. Methane is a powerful greenhouse gas, and methane released from hydrate provides a potential positive feedback mechanism in global climate change [e.g., Archer and Buffett, 2005]—in theory, the more methane is released by the hydrates, the warmer the climate gets, causing the ocean to warm and release more methane. However, methane escaping from the seabed is oxidized and dissolved in the ocean, and insufficient methane may reach the atmosphere to affect the climate significantly. Its importance for climate change therefore depends on... |
| Tipo: Text |
Palavras-chave: Methane hydrate; Svalbard; Sea floor; Seismic; Electromagnetic; Arctic. |
| Ano: 2012 |
URL: http://archimer.ifremer.fr/doc/00451/56262/57832.pdf |
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| Thatcher, K. E.; Westbrook, Graham; Sarkar, S.; Minshull, T. A.. |
| Hundreds of plumes of methane bubbles, first observed in 2008, emanate from an area of the seabed off West Svalbard that has become 1 degrees C warmer over the past 30 years. The distribution of the plumes, lying close to and upslope from the present upper limit of the methane hydrate stability zone, indicates that methane in the plumes could come from warming-induced hydrate dissociation, a process commonly invoked as contributing to rapid climate change. We used numerical modeling to investigate the response of hydrate beneath the seabed to changes in bottom-water temperature over periods of up to 1000 years B. P. The delay between the onset of warming and emission of gas, resulting from the time taken for thermal diffusion, hydrate dissociation, and gas... |
| Tipo: Text |
Palavras-chave: Methane hydrate; Gas emission; Arctic warming; Geological controls; Thermal history. |
| Ano: 2013 |
URL: http://archimer.ifremer.fr/doc/00137/24779/22838.pdf |
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